1. Field of Invention
The invention relates to a shutter, fastener, and locking mechanism that provides an easy to install means of protecting large door and window openings from hurricanes, strong winds, rain, wind-blown debris, and vandals.
2. Description of Prior Art
Studies of damage from Hurricanes Hugo, Andrew, and Iniki show that most of the damage to a home was from the wind or wind-borne missiles that broke a window and let rain and wind into the home. Once the wind was inside a home, the resulting pressure helped lift the roof off the house. Shutters can help keep the wind and rain from entering a home during strong winds.
During Hurricane warnings, plywood is usually nailed over windows and patio doors to prevent wind-driven rain and debris from breaking the window and entering the house. Nailing sheets of plywood over windows is difficult on many homes, and it could take too much time to secure a cover over each window. Strong winds can rip down nailed-up plywood; and roll-down shutters and louvered shutters are also ineffective (Fine Homebuilding, 1992).
Homeowners are usually reluctant to drive nails into their window frames or do not want to be on a ladder during high winds. An individual can not hold up a large, heavy piece of plywood and nail it in at the same time. When a hurricane is expected, often the building suppliers run out of plywood.
Plywood nailed to a window frame can be blown out of a building due to the high pressure inside a building compared to the low pressure outside during high winds. This is due to the Bernoulli effects, where wind blowing around and over a building causes lower pressure than the high pressure air inside, and sucks out a window, wall, or roof.
An airplane rises due to the pressure differential of faster air moving over a wing, compared to the high pressure of slower moving air under a wing. So too does the side walls blow out of a house due to the Bernoulli effects of wind blowing perpendicular to the wall. Gable ends blow out of a house, because of higher pressure in the house compared to the extremely low pressure on the leeward edge of the wind direction.
Once the window, side wall, or gable end of a house is blown out, the rigidity of the roof and entire house is compromised due to wind getting into the house. Driven rain, along with the wind can damage everything in the house, along with damaging the structural integrity of the roof and walls of the house.
Previously, homeowners thought that they could prevent their walls from being blown out by opening windows to relieve the high pressure on the leeward and sides of a house, but the open windows on the windward side let in wind and rain. If windows are open on the leeward side only, the wind can rapidly change direction and blow into the windows. The wind must go somewhere, and would blow out the walls or roof as it sought a way out. The resulting damage negates any advantage of trying to ease the pressure differential.
This invention is simple to install, economical, and can fit on a wide variety of houses.
The current fad of testing shutters is by shooting a 2×4 into the shutter to test its strength. This simulates a roof rafter being blown into the shutter from a neighbor's house. My previous patent application Ser. No. 08/191,852 helps keep the rafter and roof on a house, and would prevent many of these missiles.
The factual odds of a 2×4 being blown head-on into a window shutter is minuscule. Actually, a 2×4 fired headed-on into a building would go through most wood-frame and concrete-block walls. Studies after Hurricane Andrew show that the most common projectile was roof shingles and roof tiles; and when roof tiles go airborne, they damage neighboring buildings (Miller, 1992).
One advantage of this invention is that any type of covering can be used for the shutter. Plywood was used in the past because it was readily available, strong, inexpensive, easy to store, and could be cut to fit windows by most homeowners using simple tools. The major problem was with the installation.
No one wanted to be on a ladder during windy conditions, especially trying to hold the heavy plywood sheet with one hand and trying to hammer a nail with the other. That leaves no hands to hold the nail or hold on to the ladder—an unsafe situation.
Plywood can still be used as the shutter material for this invention, but steel and other stronger, lighter, and cheaper materials can be used including new materials as they become available. Researchers testing shutter material claim that thin steel walls are more effective at stopping hurricane debris than thick wood, and the most effective material was 22-gauge steel backed with a thin layer of rubber (Civil Engineering, 1994).
This is good information, but thin sheets of steel with rubber are not readily available to a homeowner. Nevertheless, if it was obtainable, it could be used as the shutter material for this invention.
When thin sheets of steel are corrugated, pleated, or formed into parallel ridges, the resulting shutter cover is stronger than flat steel. Bending the sheets of steel work-hardens it and strengthens the bends. Corrugated metal sheets, used as a shutter cover, are stronger than steel with rubber, and could withstand larger and faster wind-blown missiles. Standard corrugated steel sheets may be used with this invention as a shutter cover, but this invention includes a unique corrugated metal shutter.
Other materials can also be used for the cover such as sheets of aluminum, which are light, recyclable, strong, non-rusting, and relatively easy to cut with power equipment. Kevlar©, fiberglass, rubber sheets, or any strong, lightweight material could also be used for the cover.
Bamboo has recently been used as flooring because it is attractive, wears well, and can be sanded and refinished. Bamboo can be weaved, is flexible and can bend, and can have resins added to make a product as strong as fiberglass. Unlike timber, bamboo is a plentiful grass that regenerates itself quickly from existing root systems after being cut. Bamboo forests are not clear-cut, but are maintained by harvesting mature stalks which makes room for new shoots to grow (Home Mechanix, 1995). In the tropics, bamboo would make a good cover for a shutter and would be environmentally attractive.
Shutters should be bolted to a building (Fine Homebuilding, 1992). During Hurricane Andrew, ¾-in. plywood bolted over a window sustained several hits from tree limbs, but nothing came through (Fine Homebuilding, 1992). Even with modern weather forecasting, there would not be enough time to bolt plywood to each window of a house. This invention has brackets permanently attached to the framing members of a house for quick and easy positioning of a shutter with companion hardware.